Dispersion-correction density functional theory (DFT+D) and spin-orbit coupling (SOC) method into the structural, electronic, optical and mechanical properties of CH3NH3PbI3

Abstract

DFT simulations are used to determine the most appropriate approach to reproduce the experimental electronic structure and optical properties besides providing the reliable structural stability of CH3NH3PbI3. In this work, DFT calculations are performed using the generalized gradient approximation (GGA) that includes spin-orbit coupling (SOC) and empirical pairwise dispersion of the DFT + D method to investigate the structural, electronic, optical and mechanical properties of the material. Our results reveal that SOC effects reduced the band gap compared to GGA functional alone. Meanwhile, using the DFT + D method, an improvement in the calculation accuracy of the band gap obtained (1.689eV) is in excellent agreement with the experimental (1.630eV). Further analysis of the electronic properties demonstrates that including SOC reduces the effective masses of electrons due to the creation of splitting at the bottom of the conduction band. We have presented the absorption coefficient to describe the optical properties. It is found that CH3NH3PbI3 exhibit stronger optical absorption in the UV light region (300–400 nm). The mechanical properties of Young's modulus, bulk modulus, shear modulus and Poisson's ratio were calculated using DFT + D. It was discovered that the ratio (B/G) achieved was greater than 1.75, indicating that CH3NH3PbI3 is a ductile material.